Illinois lawmakers are in a bind over a contract to fill the prescriptions of the state’s workers. They say want to investigate the $250 million contract with Caremark Rx Inc. to see if the state is getting a good deal. But Caremark refuses to turn over its cost and pricing data.

Caremark was awarded the contract, in which it provides mail-order prescriptions to employees, after competitive bidding. Caremark says its cost and pricing structure is a trade secret that it does not want to reveal publicly, and its contract says that the state will keep it confidential. When local pharmacies in competition with Caremark claimed that the state was paying too much, lawmakers wanted to wanted to investigate and asked for the data.

Caremark offered to provide it to lawmakers who pledged to keep it confidential, but the Solons demurred. Two of them will go to court Friday to argue that the pricing data must be revealed under the Illinois Freedom of Information Act.